Storage time dependent photodissociation action spectroscopy of polycyclic aromatic hydrocarbon cations in the cryogenic electrostatic storage ring DESIREE

Stockett, Mark H.; Björkhage, Mikael; Cederquist, H.; Schmidt, H. T.; Zettergren, Henning

doi:10.1039/c8fd00161h

Cited by 20 publications

(22 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Finally, a helium (He) gas pulse is injected 5 s after the ion selection and 15 s before the VUV irradiation. Collisions of the trapped ions with He atoms cooled by collisions with the cryogenic walls is found to improve ion cooling (Stockett et al 2019).…”

Section: Experimental Methodsmentioning

confidence: 99%

Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions

Marciniak

Joblin

Mulas

et al. 2021

A&A

View full text Add to dashboard Cite

Context. The interaction of polycyclic aromatic hydrocarbons (PAHs) with vacuum ultraviolet (VUV) photons triggers the emission of the well-known aromatic infrared bands (AIBs), but other mechanisms, such as fragmentation, can be involved in this interaction. Fragmentation leads to selection effects that favor specific sizes and structures. Aims. Our aim is to investigate the impact of aliphatic bonds on the VUV photostability of PAH cations in a cryogenic and collisionless environment with conditions applicable for photodissociation regions (PDRs). Methods. The studied species are derived from pyrene (C16H10) and coronene (C24H12) and contain aliphatic bonds either in the form of methyl or ethyl sidegroups or of superhydrogenation. Their cations are produced by laser desorption ionization and isolated in the cryogenic ion cell of the PIRENEA setup, where they are submitted to VUV photons of 10.5 eV energy over long timescales (~1000 s). The parent and fragment ions are mass-analyzed and their relative intensities are recorded as a function of the irradiation time. The fragmentation cascades are analyzed with a simple kinetics model from which we identify fragmentation pathways and derive fragmentation rates and branching ratios for both the parents and their main fragments. Results. Aliphatic PAH derivatives are found to have a higher fragmentation rate and a higher carbon to hydrogen loss compared to regular PAHs. On the other hand, the fragmentation of PAHs with alkylated sidegroups forms species with peripheral pentagonal cycles, which can be as stable as, or even more stable than, the bare PAH cations. This stability is quantified for the main ions involved in the fragmentation cascades by the comparison of the fragmentation rates with the photoabsorption rates derived from theoretical photoabsorption cross sections. The most stable species for which there is an effective competition of fragmentation with isomerization and radiative cooling are identified, providing clues on the structures favored in PDRs. Conclusions. This work supports a scenario in which the evaporation of nanograins with a mixed aliphatic and aromatic composition followed by VUV photoprocessing results in both the production of the carriers of the 3.4 μm AIB by methyl sidegroups and in an abundant source of small hydrocarbons at the border of PDRs. An additional side effect is the efficient formation of stable PAHs that contain some peripheral pentagonal rings. Our experiments also support the role of isomerization processes in PAH photofragmentation, including the H-migration process, which could lead to an additional contribution to the 3.4 μm AIB.

show abstract

Section: Experimental Methodsmentioning

confidence: 99%

Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions

Marciniak

Joblin

Mulas

et al. 2021

A&A

View full text Add to dashboard Cite

show abstract

“…As part of this study, we developed a simple harmonic cascade (SHC) model of infrared radiative cooling, which satisfactorily described the experimental data. A similar twodimensional action spectroscopy strategy to probe cooling dynamics, although using Multi-Photon Dissociation, has been applied to probe the radiative cooling of Polycyclic Aromatic Hydrocarbon cations [29].…”

Section: Introductionmentioning

confidence: 99%

Radiative cooling of carbon cluster anions C2n+1− (n = 3–5)

et al. 2020

Self Cite

View full text Add to dashboard Cite

Radiative cooling of carbon cluster anions C2n+1− (n = 3–5) is investigated using the cryogenic electrostatic ion storage ring DESIREE. Two different strategies are applied to infer infrared emission on slow (milliseconds to seconds) and ultraslow (seconds to minutes) timescales. Initial cooling of the ions over the millisecond timescale is probed indirectly by monitoring the decay in the yield of spontaneous neutralization by thermionic emission. The observed cooling rates are consistent with a statistical model of thermionic electron emission in competition with infrared photon emission due to vibrational de-excitation. Slower cooling over the seconds to minutes timescale associated with infrared emission from low-frequency vibrational modes is probed using time-dependent action spectroscopy. For C9− and C11−, cooling is evidenced by the time-evolution of the yield of photo-induced neutralization following resonant excitation of electronic transitions near the detachment threshold. The cross-section for resonant photo-excitation is at least two orders of magnitude greater than for direct photodetachment. In contrast, C7− lacks electronic transitions near the detachment threshold. Graphical abstract

show abstract

“…This will be a strong limitation in the survival of these species in the photon-irradiated regions where these species are possibly present. On the laboratory side, the availability of cryogenic ion storage ring opens the possibility to record the photodissociation spectrum in a wide storage time range up to several seconds at which the dimer ions are expected to be colder due to IR emission (60). On the theoretical side, the present study illustrates the possibility for the DFTB-derived scheme, DFTB-EXCI, to account for the electronic spectroscopy of cationic molecular clusters when relatively large molecules and high electronic states are involved, despite the inherent approximations of the method.…”

Section: Discussionmentioning

confidence: 99%

Experimental and theoretical study of photo-dissociation spectroscopy of pyrene dimer radical cations stored in a compact electrostatic ion storage ring

Bernard

Al‐Mogeeth

Martin

et al. 2021

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

Storage time dependent photodissociation action spectroscopy of polycyclic aromatic hydrocarbon cations in the cryogenic electrostatic storage ring DESIREE

Abstract: The intrinsic absorption profile and radiative cooling rate of coronene cations are reported.

Cited by 20 publications

References 35 publications

Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions

Photodissociation of aliphatic PAH derivatives under relevant astrophysical conditions

Radiative cooling of carbon cluster anions C2n+1− (n = 3–5)

Experimental and theoretical study of photo-dissociation spectroscopy of pyrene dimer radical cations stored in a compact electrostatic ion storage ring

Contact Info

Product

Resources

About